Re: Backref in a regex quantifier

I don't think you will be able to do this in one step, you will probably have to do something like this:

if ( /^(\d+?)/ ) {
    my $len = $1;
    if ( /^$len(.{$len})/ ) {
        my $value = $1;
        # do something with $len and $value
    }
}
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We're not surrounded, we're in a target-rich environment!

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Re^2: Backref in a regex quantifier by webfiend (Vicar) on Jul 09, 2007 at 18:10 UTC
Here's a marginally more clever version of your solution, which relies on the placeholder capabilities of a /g search. I mention it because I think it's a tiny bit more readable than the version you wrote. But ... you know ... personal preference and all that. `use strict; use warnings; my $test_string = "3 xyz"; # Start a global search # It looks like the expected pattern includes a space. Let's put it he +re. if ( $test_string =~ m/^(\d+) /g ) { my $length = $1; # Pick up the search where our first match left off. if ( $test_string =~ m/\G(.{$length})/ ) { my $result = $1; # Do stuff with $result ... } }` [download]	[reply] [d/l]

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Re^2: Backref in a regex quantifier
by webfiend (Vicar) on Jul 09, 2007 at 18:10 UTC

Here's a marginally more clever version of your solution, which relies on the placeholder capabilities of a /g search. I mention it because I think it's a tiny bit more readable than the version you wrote. But ... you know ... personal preference and all that.

use strict;
use warnings;

my $test_string = "3 xyz";

# Start a global search
# It looks like the expected pattern includes a space. Let's put it he
+re.
if ( $test_string =~ m/^(\d+) /g ) {
    my $length = $1;

    # Pick up the search where our first match left off.
    if ( $test_string =~ m/\G(.{$length})/ ) {
        my $result = $1;
        # Do stuff with $result ...
    }
}
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