$s= 'ABCDEFG'
$s =~ s// /g
print "'$s'"
' A B C D E F G '

##</code><code>##

$s= 'ABCDEFG'
$s =~ s/^/prefix-/
print $s
prefix-ABCDEFG
$s =~ s/$/-postfix/
print $s
prefix-ABCDEFG-postfix