$ cat 930256_a.pl
#!/usr/bin/perl
use strict;
use warnings;

#my @list = (5, undef, 1 .. 9);
my @list = (5, 1 .. 9);

sub xmap {
    my $match = shift;
    my $rc = shift;
    my @rv=();
    for (@_) {
        push @rv, &$rc($_);
        last if $_ eq $match;
    }
    return @rv;
}

print "list: ", join(", ", @list), ".\n";
print "xmap: ", join(", ", xmap(7, sub { $_*2 }, @list)),".\n";

$ perl 930256_a.pl
list: 5, 1, 2, 3, 4, 5, 6, 7, 8, 9.
xmap: 10, 2, 4, 6, 8, 10, 12, 14.