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unshift

Perl 5 version 20.1 documentation
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unshift

  • unshift ARRAY,LIST

  • unshift EXPR,LIST

    Does the opposite of a shift. Or the opposite of a push, depending on how you look at it. Prepends list to the front of the array and returns the new number of elements in the array.

    1. unshift(@ARGV, '-e') unless $ARGV[0] =~ /^-/;

    Note the LIST is prepended whole, not one element at a time, so the prepended elements stay in the same order. Use reverse to do the reverse.

    Starting with Perl 5.14, unshift can take a scalar EXPR, which must hold a reference to an unblessed array. The argument will be dereferenced automatically. This aspect of unshift is considered highly experimental. The exact behaviour may change in a future version of Perl.

    To avoid confusing would-be users of your code who are running earlier versions of Perl with mysterious syntax errors, put this sort of thing at the top of your file to signal that your code will work only on Perls of a recent vintage:

    1. use 5.014; # so push/pop/etc work on scalars (experimental)