print backslash in variable

palinurus has asked for the wisdom of the Perl Monks concerning the following question:

I need to know, how many backslashes are in a variable, but with 'print' it gives me unclear output on the Linux console. I use the following code:

$i1 = '1\2';
$i2 = '1\\2';
$i3 = '1\\\2';
$i4 = '1\\\\2';
print "#$i1#$i2#$i3#$i4#\n";
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It gives me the following output:

#1\2#1\2#1\\2#1\\2#
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The first 2 and the last 2 variables give the same output. But I must know, how many backslashes in a row are in the variable. Any hints?

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Re: print backslash in variable by hippo (Archbishop) on Aug 17, 2015 at 16:06 UTC
The method you are using to set the variables (enclosing in single quotes) means that the backslashes are escaped by other backslashes. Your print statement is a good idea and is genuinely showing you the correct values of the variables. A quick read of Quote and Quote-like Operators may help to clear things up for you.	[reply]
Re^2: print backslash in variable by soonix (Chancellor) on Aug 18, 2015 at 08:28 UTC
... more exactly, first entry in subsection Quote-Like Operators (without "Quote and"). I guess this (and the "Regexp" and "Gory details" sections) should be subheadings under "Quote and Quote-like".	[reply]
Re: print backslash in variable by AnomalousMonk (Archbishop) on Aug 17, 2015 at 17:16 UTC
... I must know, how many* backslashes in a row ...* A way: `c:\@Work\Perl\monks>perl -wMstrict -le "my $s = '\\\\\---\--\\\\---\\--\\\-'; print qq{'$s'}; ;; printf ' %d', $_ for map tr{\\}{}, $s =~ m{ \\+ }xmsg; " '\\\---\--\\---\--\\-' 3 1 2 1 2` [download] Update: map expression was `scalar(tr{\\}{\\})` but I realized scalar wasn't necessary. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]
Re: print backslash in variable by johngg (Canon) on Aug 17, 2015 at 21:47 UTC
You could initialise your variables using the `\x??` hexadecimal character values to avoid confusion. $ perl -E ' say for ( qq{a\x5cb}, qq{a\x5c\x5cb}, qq{a\x5c\x5c\x5cb}, qq{a\x5c\x5c\x5c\x5cb}, );' a\b a\\b a\\\b a\\\\b $ [download] I hope this is helpful. Update: Another way would be to use chr. `$ perl -E ' > @arr = map { q{A} . do { chr 0x5c } x $_ . q{B} } 1 .. 4; > say for @arr;' A\B A\\B A\\\B A\\\\B $` [download] Cheers, JohnGG	[reply] [d/l] [select]