Altho' perfectly correct, methinx that the simple for loop construct you use is more normally written as

push @ret, $coderef->() for @params;
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In fact, simpler still would be use the incoming arg list directly and to use parens for the non-core call to foo (as per PBP) ...

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

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

    push @ret, $coderef->() for @_;

    return @ret;
}

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