Leocharre, you're right on in being cautious of the truth of the loop condition. Which is necessary due to the lack of while(<>)-style magic in a mere while($_=shift){}.

Consider how the usual looping variants work or mostly fail, or just ask Perl with a simple, cute and short one-liner:

perl -e 'use Data::Dumper; @a=(1,0,undef,2); print Dumper(@a); print "
+1=$_=\n" foreach (@a); @ARGV=@a; print "2=$_=\n" while($_=shift @a); 
+@a=@ARGV; print "3=$_=\n" while($_=shift @a,defined $_); @a=@ARGV; pr
+int "4=$_=\n" while($_=shift);'

[download]
<Reveal this spoiler or all in this thread>

PS: ad local: local($_) helps to not hurt the caller (but isn't e.g. necessary in a foreach(@a) scope), while my($_) (since 5.10) helps the current scope to not be hurt by called routines (and signal handlers, etc).

\Peter, who is wondering whether the line-eater did like the taste of his attempted .sig

In reply to Re: using shift and $_ in loop by jakobi
in thread using shift and $_ in loop by leocharre

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