$ cat ta.pl
#!/usr/bin/perl

use strict;
use warnings;

my @oldlist = qw X /etc/passwd /etc/group /egg/drop /etc/shadow X;

print "\nBefore map (oldlist)\n";
print "==========\n";
foreach (@oldlist) {
    print "$_\n";
}
my @newlist = map  s/\/etc\/// ,  @oldlist;

print "\nAfter map (oldlist)\n";
print "=========\n";
foreach (@oldlist) {
    print "$_\n";
}
print "\nAfter map (newlist)\n";
print "=========\n";
foreach (@newlist) {
    print "$_\n";
}

$ ./ta.pl

Before map (oldlist)
==========
/etc/passwd
/etc/group
/egg/drop
/etc/shadow

After map (oldlist)
=========
passwd
group
/egg/drop
shadow

After map (newlist)
=========
1
1

1
$