In Perl you can use regular expressions and the substitution function to transform a string:

$somestring -- is the string to be acted upon. A string is a bunch of character "strung" together likes beads on a "string". Hence the name. The sentence is "string" made up of individual letters "characters".

=~ -- a strange function which translate into something like "let the expression on the left be modified by the equation on the right and become that transformed thing". Obviously that is quite a mouthful so those crazy unix type dude use "=~".

s -- The s operator searches the string passed to it for items matching the regular expression defined by old and then replaces all instances with new.

old -- the regular expression that "s" looks for.

new -- the stuff to substitute wherever "old" was found.

g -- an option flag telling "s" to do the operation on the whole string.

; -- the infamous semi-colon that we still forget sometimes.

So let's try this: