Re: creating qr from existing regex

Remove the slashes, extract the modifier ("i") (say, in a variable $flags). Keep the core of the regex as a string, in your example that would be .*uba$.

Then put "(?$flags:" in front of it, and ")" behind it. You can use that string ($re) directly as a regex:

$re = "(?:$flags:$core)";
if($input =~ $re) { ... }
[download]

edit Oops, one too many colons:

$re = "(?$flags:$core)";
if($input =~ $re) { ... }
[download]

You can also turn it into a regex object:

$qr = qr/$re/;
[download]

Comment on Re: creating qr from existing regex Select or Download Code

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Re^2: creating qr from existing regex by AnomalousMonk (Archbishop) on Feb 09, 2018 at 21:07 UTC
`$re = "(?:$flags:$core)";` That doesn't work: too many `':'` (colons): `c:\@Work\Perl\monks>perl -wMstrict -le "my $string = '/.uba$/i'; ;; my $flag = qr{ [msixpodual] }xms; ;; my $convertable = my ($core, $flags) = $string =~ m{ \A \s / (.?) / ($flag) \z }xms; die qq{bad rx: '$string'} unless $convertable; ;; my $re = qq{(?:$flags:$core)}; print $re; print 'A: match' if 'uba' =~ $re; " (?:i:.uba$)` [download] Something like this works: c:\@Work\Perl\monks>perl -wMstrict -le "my $string = '/.u\/ba$/i'; ;; my $flag = qr{ [msixpodual] }xms; ;; my $convertable = my ($pattern, $modifiers) = $string =~ m{ \A \s* / (.?) / ($flag) \z }xms; die qq{bad rx: '$string'} unless $convertable; ;; my $rx = qr{(?$modifiers)$pattern}; print $rx; print 'A: match' if 'u/Ba' =~ $rx; ;; my $ry = qr{ \A foo $rx }xms; print $ry ;; print 'B: match' if 'foolubatU/bA' =~ $ry; print 'C: match' if 'FoolubatU/bA' =~ $ry; " (?^:(?i).u\/ba$) A: match (?^msx: \A foo (?^:(?i).u\/ba$) ) B: match [download] Note that: I go directly to `qr//` form. The modifiers (`$flag` pattern) implemented vary by Perl version; see perlop. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re^3: creating qr from existing regex by bart (Canon) on Feb 12, 2018 at 11:47 UTC
Yes, `"(?:$flags:$pattern)"` is wrong, it should have been `"(?$flags:$pattern)"`. That is: the flags between the leading "`(?`" and "`:`" of the standard non-capturing grouping parens, i.e. "`(?:$pattern)`". You can always try to print out a `qr/foo/i`, to see what perl does natively.	[reply] [d/l] [select]


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