#!/usr/bin/env perl
use 5.010;
use strict;
use warnings;

sub foo(&@) {
    my $coderef = shift;
    my @params = @_;
    my @ret;

    while(@params) {
        push @ret, $coderef->($_);
    }
    return @ret;
}

my @a = ( "1", "2", "3", "4", );
my @b = foo { $_ ** 2 } @a;