## Given string, needs to squeze
my $string = "squeezing spaces fro m t h e string";
## regex that squeeze the spaces
$string =~ s/\s//g;
print "$string \n";
Here \s means the space. Wherever any space found from the string it will be replaces with empty('').
If you think you need to remove other character, not the space. Then you can squeeze the string with that character too. For example you need to squeeze all the a's from the string. Just replace the \s with a, and it will replace all a's into empty(''). Example code.
$string =~ s/a//g;
If you need to squeeze with multiple characters. You can use all chars inside  and it will remove any character that will found inside . For example you need to squeeze for space, a, b and c. Then inside then it will be [\sabc]. \s for space.
$string =~ s/[\sabc]//g;
You can separate the characters with pipe(|) too instead of inside . For example
$string =~ s/\s|a|b|c//g;
Thats all for today. Hope you enjoyed the article. For more you can take a look at my blog http://icfun.blogspot.com/search/label/perl