Re: my $var = join('|',@array) not behaving

[grep]

Square brackets [] are for creating a reference to an anonymous array. Parens () construct a list which you can assign to an array.
You can read more at perldata and perlref

Try This:

my @array = ( 1, "word", 2 );
my $print_string = join ('|', @array);
print "$print_string\n";

[chromatic]

Parens () construct a list which you can assign to an array.

Nit: parens group a list. The list is already there, but the precedence of = and , are such that without parentheses, only the first element of the list gets assigned.

[ikegami]

such that without parentheses, only the first element of the list gets assigned.

Since we're being picky about the language, the list being assigned only has one element, so it's odd to refer to its first element. The assignment is the first element of the larger list.