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Re^3: skipping the first line of a file

by johngg (Canon)
on Jun 12, 2009 at 22:39 UTC ( #771130=note: print w/replies, xml ) Need Help??

in reply to Re^2: skipping the first line of a file
in thread skipping the first line of a file

my ... for ...; is not valid Perl.

Well, it seems to compile and run with no warnings or errors.

use strict; use warnings; my $discard = <DATA> for 1 .. 2; print while <DATA>; __END__ Header 1 Header 2 Data 1 Data 2 Data 3
$ ./spw770971 Data 1 Data 2 Data 3 $

Please could you explain in what way it is not valid.



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Re^4: skipping the first line of a file
by ikegami (Patriarch) on Jun 13, 2009 at 20:11 UTC

    Because the docs says it isn't.

    The behaviour of a my statement modified with a statement modifier conditional or loop construct (e.g. my $x if ... ) is undefined. The value of the my variable may be undef, any previously assigned value, or possibly anything else. Don't rely on it. Future versions of perl might do something different from the version of perl you try it out on. Here be dragons.

    ( EmphasisStrong emphasis in original. )

    That said, the current behaviour is actually quite predictable, and it doesn't limit $discard to the loop

    >perl -cwe"use strict; my $x for 1..2; print $x" -e syntax OK

    So not only is not valid Perl, it doesn't even work.

      You learn something new every day. I'll remember not to do that in future but use a real loop instead.

      Thank you,


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