Perl Strings

# till end of line is a comment, and is equvalent to whitespace.

= at start of a line where a statement would be legal is igorned up to line that says =cut.
Called POD (Plain Old Documentation).

"Here" documents are like shell based syntax. Following a << (no space) specify a string to terminate the quoted material, for example:

print <<EOF
The price is the $Price.
...
EOF
; # essential to not get results combined with next statement!

A word that hos no other interpretation in the grammar is treated as if it were a quoted string. These are called barewords, e.g.
   @days = (Mon,Tue,Wed,Thu,Fri);
Because this is error prone, use the following to disable it:
   use strict 'subs';
in which case any bareword not interpreted as a subroutine call produces a compile-time error. The restriction lasts to the end of the enclosing block. An inner block can countermand by saying:
   no use strict 'subs';

Customary	Generic	Meaning	Substitute Interpolate
''	q//	Literal	No
""	qq//	Literal	Yes
``	qx//	Command	Yes
()	qw//	Word List	No
//	m//	Pattern Match	Yes
s//	s//	Substitution	Yes
y//	tr//	Translation	No

Note the generic form can use any character as the delimiter, e.g. ! or | , but if it has a symmetry then the opposite one must be used to close: ( ) [ ] { } < >.