CODEWITHSUNDEEP
perl
Sam Pinar
Sam Pinar

Reputation: 43

perl file test operators and "$_"

I'm going through O'Reilly's "Intermediate Perl". -s is used as so:

print map { "    $_\n" } grep { -s < 1000 } @ARGV;

which gives this warning:

Warning: Use of "-s" without parentheses is ambiguous Unterminated <> operator

Though, when I put parentheses around -s it works like a charm. Not sure if this is perl version related or a mistype by authors.

Perl version: v5.18.2 built for darwin-thread-multi-2level

What is causing this issue and what I can do to correct it?

Upvotes: 1

Views: 206

Answers (1)

ikegami
ikegami

Reputation: 385635

< can be the start of a term as the readline/glob shortcut.

print "[$_]\n" for < a b c >;

< can be the start of an infix operator as the numeric less-than operator.

print "foo\n" if $x < 3;

-s can legally be followed by both, so Perl has to guess which one you wanted when it sees the <. Using any of the following instead of -s solves the issue since none of them can be followed by a term:

  • -s($_)
  • -s()
  • (-s)

Upvotes: 2

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