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.

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.