Passing qr/\s+/ into a subroutine as a delimiter for split seems to cause a subsequent call to that function to fail in v5.6.1

[p5pRT]

Migrated from rt.perl.org#30505 (status was 'resolved')

Searchable as RT30505$

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From joseph.reel@citigroup.com

In Perl 5.6.1 the following script

#!/opt/mr/perl/bin/perl -w
use strict;

my @​c = test ("dealloans dat", qr/\s{1,256}/);
my @​d = test ("dealloans|dat", qr/\|/);
print "@​c\n";
print "@​d\n";

sub test {
  my ($data, $delim) = @​_;
  my @​d = split /$delim/, $data;
  return @​d;
}

results in output

dealloans dat
dealloans dat

as expected, but replacing qr/\s{1,256}/ above with qr/\s+/ gives output

dealloans dat
dealloans|dat

so it looks like the second subroutine call fails.

[p5pRT]

From @hvds

"Reel, Joseph \[FI\]" (via RT) <perlbug-followup@​perl.org> wrote​:
:In Perl 5.6.1 the following script
:
:#!/opt/mr/perl/bin/perl -w
:use strict;
:
:my @​c = test ("dealloans dat", qr/\s{1,256}/);
:my @​d = test ("dealloans|dat", qr/\|/);
:print "@​c\n";
:print "@​d\n";
:
:sub test {
: my ($data, $delim) = @​_;
: my @​d = split /$delim/, $data;
: return @​d;
:}
:
:results in output
:
:dealloans dat
:dealloans dat
:
:as expected, but replacing qr/\s{1,256}/ above with qr/\s+/ gives output
:
:dealloans dat
:dealloans|dat
:
:so it looks like the second subroutine call fails.

Thanks for the report. This bug has been fixed in perl-5.8.0 and later
releases.

I suspect that in 5.6.1 there may be a specific optimisation for
split(/\s+/, ...) implemented by modifying the compiled split() node
itself, but failing to ensure that the optimisation was applied only
when the pattern was supplied as a constant.

If you need a specific workaround for 5.6.1, it looks as if you can
defeat the optimisation by including something extra when you incorporate
the supplied pattern, eg​:
  my @​d = split /$delim(?=)/, $data;
.. but this will defeat many optimisations, and may therefore have a
noticeable runtime cost.

Hugo

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