Single, double and back quotes

Initial String Handling example from a Well House Consultants training course
More on Initial String Handling [link]

This example is described in the following article(s):
• Seven new intermediate Perl examples - [link]

Source code: dqs Module: P205

=head1 Single, Double and backquoted strings

In Perl, you can write ...
* A literal string in single quotes
* A string in which \ $ and @ are expanded in double quotes
* An operaring systems command to be run in backquotes
and in each case, the result will be returned to you as the
result of the operation if you want to save it into a variable.

If you really want a double quote character within a double
quoted string, you can always add an extra \ in front of it -
but that facility is NOT similarly available to you if you
want a single quote in a single quoted string. So you have
to use the alternatives ...
* qq followed by any non-alphanumeric delimter of your choice
gives you a double quoted string
* q followed by any non-alphanumeric delimter of your choice
gives you a single quoted string
* qx followed by any non-alphanumeric delimter of your choice
gives you a shell executed command

Finally, you can write multiline strings in what are know as
"here" documents, where the delimiter is a complete string and
must occur further down on a line ON ITS OWN (no ;, no spaces)
to indicate the end of the block.

=cut

$bairn = "Rebecca";
$boyfriend = 'Damian';
$pet = "Dog";

# Single quote, + delimited
print q+"Don't wash the $pet" said $bairn to $boyfriend\n+;
# Double quote, { to } delimited
print qq{"Don't wash the $pet" said $bairn to $boyfriend\n};

# here document - double quoted string
print <<"ZsL";
"Don't wash the $pet" yelled $bairn at $boyfriend. "I know
you want to, but you haven't finished the dishes yet and the
Augian Stables need mucking out too" ....
ZsL

# quote and execute, ! delimited
$report = qx!uptime!;
print $report;

$whom = "Salvatore";
# here document for a whole block of shell
$report = <<`COCKLE`;
ls -ld .
pwd
date
grep -c $whom *
uptime
df -k
COCKLE

print $report;

__END__

Results sample:

Dorothy:p82 grahamellis$ perl dqs
"Don't wash the $pet" said $bairn to $boyfriend\n"
Don't wash the Dog" said Rebecca to Damian
"Don't wash the Dog" yelled Rebecca at Damian. "I know
you want to, but you haven't finished the dishes yet and the
Augian Stables need mucking out too" ....
7:20 up 25 mins, 2 users, load averages: 0.15 0.11 0.14
drwxr-xr-x 44 grahamellis grahamellis 1496 30 Oct 07:20 .
/Users/grahamellis/p82
Thu 30 Oct 2008 07:20:40 GMT
1:0
PP.book.pdf:0
ck:0
demo:0
din:0
dothis:0
dqs:1
four:0
four2:0
[etc .... ]
wi:0
wim:0
wim0:0
zt:0
7:20 up 25 mins, 2 users, load averages: 0.15 0.11 0.14
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/disk0s3 117089712 84455608 32378104 73% /
devfs 105 105 0 100% /dev
fdesc 1 1 0 100% /dev
map -hosts 0 0 0 100% /net
map auto_home 0 0 0 100% /home
Dorothy:p82 grahamellis$

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