split join

 split, which breaks up a string ac-cording to a pattern.
@fields = split /separator/, $string;
The default for split is to break up $_ on whitespace:
my @fields = split;  # like split /\s+/, $_;

@fields = split /:/, "abc:def:g:h";  # gives ("abc", "def", "g", "h")
You could even have an empty field, if there were two delimiters together:
@fields = split /:/, "abc:def::g:h";  # gives ("abc", "def", "", "g", "h")
Here’s a rule that seems odd at first, but it rarely causes problems: leading empty fields
are always returned, but trailing empty fields are discarded. For example:‖
@fields = split /:/, ":::a:b:c:::";  # gives ("", "", "", "a", "b", "c")


A "split" on "/\s+/" is like a "split(' ')" except that any leading
               whitespace produces a null first field.  A "split" with no
               arguments really does a "split(' ', $_)" internally.

$str = "  10 30 st mmmmm    ";

@f = split /\s+/, $str;
print "@f\n";

@s = split(' ', $str);
@d = split(' ', $str);
print "@s\n";
print "@d\n";

# 10 30 st mmmmm
#10 30 st mmmmm
#10 30 st mmmmm

join glues together a bunch of pieces to make a single string. The join function looks like this:
my $result = join $glue, @pieces;