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PerlMonks |
in reply to Matching against $_ behaves differently than matching against a named scalar?
my $line; while ($line = <>) { ...
With the declaration inside the condition, it's in fact a different variable every time, so Perl needs to create an extra scope for it, as B::Deparse shows you:
$ perl -MO=Deparse -e 'while (<>) { /(.)/ }' while (defined($_ = readline ARGV)) { /(.)/; } -e syntax OK $ perl -MO=Deparse -e 'while (my $line = <>) { $line =~ /(.)/ }' while (defined(my $line = readline ARGV)) { do { $line =~ /(.)/ }; } -e syntax OK
Also note that lines containing 0 as their first or second word are not printed.
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