Grrr! I wish they wouldn't do that.

Anticipating more ante upping, with deeply nested brace/bracket combos and wanting to capture a nested (but not an isolated) '{}' or '[]', e.g. '{ {} }', here's (maybe) a bit of a cheat: 

#!/usr/bin/env perl -l

use strict;
use warnings;

my ($brace_re, $bracket_re);
$brace_re = qr< { (?: [^{}]++ | (??{ $brace_re }) )* } >x;
$bracket_re = qr< \[ (?: [^\[\]]++ | (??{ $bracket_re }) )* \] >x;
my $re = qr< ( $brace_re | $bracket_re ) >x;

while (<DATA>) {
    print;
    while (/$re/g) {
        print "MATCH = $1" if length $1 > 2;
    }
    print '-' x 60;
}

__DATA__
...?[](...$[] = [ USER_ENTITY_NAME ], text${} = { this is a test })...
a[] = [ this is a [ test ] { test2 } ]
a{} = { this is a { test } [ test2 ] }
{ a { b [ {}c{} ] d } e } = [ f [ g { []h[] } i ] j ]
{}[]{ {}[] }[]{} - []{}[ []{} ]{}[]

[download]

Output:

...?[](...$[] = [ USER_ENTITY_NAME ], text${} = { this is a test })...

MATCH = [ USER_ENTITY_NAME ]
MATCH = { this is a test }
------------------------------------------------------------
a[] = [ this is a [ test ] { test2 } ]

MATCH = [ this is a [ test ] { test2 } ]
------------------------------------------------------------
a{} = { this is a { test } [ test2 ] }

MATCH = { this is a { test } [ test2 ] }
------------------------------------------------------------
{ a { b [ {}c{} ] d } e } = [ f [ g { []h[] } i ] j ]

MATCH = { a { b [ {}c{} ] d } e }
MATCH = [ f [ g { []h[] } i ] j ]
------------------------------------------------------------
{}[]{ {}[] }[]{} - []{}[ []{} ]{}[]

MATCH = { {}[] }
MATCH = [ []{} ]
------------------------------------------------------------

[download]

Update: For Perl v5.8, you'll need to change [...]++ to (?> [...]+ ) (the '++' appeared in v5.10) and qr<...> delimiters will need to be something else, e.g. qr!...!.

The '(??{ $re })' construct has been around since at least v5.8.8.

Here's the perlre doco for 5.8.8 and 5.10.0.

-- Ken

In reply to Re^3: Regular expressions: Extracting certain text from a line by kcott
in thread Regular expressions: Extracting certain text from a line by Wcool

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