Perl

Regular Expression with Capture Groups

See more Regular Expressions Examples

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Demonstrates the following PCRE2 regular expression:

See the sample code below.

Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)

And apply it to this string:

Name: John Smith, Email: john.smith@example.com

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Regex Components Explained

Part	Meaning	Matched Text
"Name:"	Matches the literal text "Name:"	"Name:"
"\s+"	Matches one or more whitespace characters (spaces, tabs, etc.)	(space)
"(\w+)"	Capture Group 1: One or more word characters ("a-zA-Z0-9_")	"John"
"\s+"	More whitespace	(space)
"(\w+)"	Capture Group 2: Another word (the last name)	"Smith"
","	A literal comma	","
"\s+"	Whitespace again	(space)
"Email:"	Matches the literal "Email:"	"Email:"
"\s+"	Whitespace	(space)
"(\S+)"	Capture Group 3: One or more non-whitespace characters	"john.smith@example.com"

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Matches for Your Example String

String:

"Name: John Smith, Email: john.smith@example.com"

Regex Match Groups:

Group	Captured Value
Group 1	"John"
Group 2	"Smith"
Group 3	"john.smith@example.com"

---

Notes on Character Classes

• \w matches [a-zA-Z0-9_] — so it doesn’t include punctuation like a period.
• \S matches any non-whitespace character, so it’s good for capturing an email.

Perl

use chilkat();

$success = 0;

$subject = 'Name: John Smith, Email: john.smith@example.com';
$pattern = "Name:\\s+(\\w+)\\s+(\\w+),\\s+Email:\\s+(\\S+)";

$sb = chilkat::CkStringBuilder->new();
$sb->Append($subject);

$json = chilkat::CkJsonObject->new();
$json->put_EmitCompact(0);

$timeoutMs = 2000;
$numMatches = $sb->RegexMatch($pattern,$json,$timeoutMs);
if ($numMatches < 0) {
    # Probably an error in the regular expression.
    # Suggestion: Use AI to help create and/or diagnose regular expressions.
    print $sb->lastErrorText() . "\r\n";
    exit;
}

# Examine the matches:
print $json->emit() . "\r\n";

# This is the JSON with the match information.
# See the JSON parsing code below to get the matched capture group values.

# Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

# {
#   "match": [
#     {
#       "group": [
#         {
#           "cap": "Name: John Smith, Email: john.smith@example.com",
#           "idx": 0,
#           "len": 47
#         },
#         {
#           "cap": "John",
#           "idx": 6,
#           "len": 4
#         },
#         {
#           "cap": "Smith",
#           "idx": 11,
#           "len": 5
#         },
#         {
#           "cap": "john.smith@example.com",
#           "idx": 25,
#           "len": 22
#         }
#       ]
#     }
#   ]
# }

$i = 0;
$matchCount = $json->SizeOfArray("match");
while ($i < $matchCount) {
    print "Match " . ($i + 1) . ":" . "\r\n";
    $json->put_I($i);
    $j = 0;
    $numCaptureGroups = $json->SizeOfArray("match[i].group");
    while ($j < $numCaptureGroups) {
        $json->put_J($j);
        $cap = $json->stringOf("match[i].group[j].cap");
        print $j . ": " . $cap . "\r\n";
        $j = $j + 1;
    }

    $i = $i + 1;
}

# Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

# Output

# Match 1:
# 0: Name: John Smith, Email: john.smith@example.com
# 1: John
# 2: Smith
# 3: john.smith@example.com