I threw some debug-foo at this code fragment and came up with yes and no. Looking at the code via B::Concise it looks like the regex is compiled each time. Looking at the code view use re 'debug' it looks like it's compiled only once. I suppose that enough digging through perl's guts would provide a real answer but really -- I'd rather just use qr to control when the regex is compiled and not have to worry about what the internals are doing.

I mean, there are times it's interesting and useful to know what's happening but this case is just too opaque to get at.

my @in = qw(nc01123.log
            nc02123.log
            nc03123.log);
my $year = '0';
my $month = '2';
@in = grep { /^nc$year$month.*\.log$/ } @in;
print "@in\n";
__END__

Try zero: The nested sub block was hard to read so this didn't yield t
+oo much.
perl -MO=Concise test.pl

Try one: This makes it look like the regex is compiled anew each time.
perl -MO=Concise,-exec test.pl

Try two: This looks like the regex is compiled only once. Or maybe deb
+ug just <i>dumps</i> it once.
use re 'debug';

[download]

Fun Fun Fun in the Fluffy Chair

In reply to Re^7: Grep Pattern Match by diotalevi
in thread Grep Pattern Match by LostS

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