I have a file with lines of the form

/dev/sda4 6 Fri Apr 12 04:30:02 2019 +0100   /dumpx/DUMP4X/var/level6/55    86.53 MB

and I have another file with lines of the form

/dumpx/DUMP4X/var/level6/55

and I would like to find (and remove) all the lines in the first file which contain the strings in the second file. Fortunately, I can assume that both files are sorted in the same order.

to find a single entry is simple:

if $line =~ m?/dumpx/DUMP4X/var/level6/55? then do something

but what I want to do is to read lines from the two files in a suitable loop, picking out the matches, so I need a $regexp variable

So I write

$regexp = "m?" . <STDIN> . "?";

(the second file is actually coming from a pipe)

and then I test

if $line =~ $regexp ...

and if it matches, then I do the necessary stuff, and fetch the next $line and obtain the next $regexp.

But the =~ operator has been cunningly designed so that does not work. Essentially, if the RHS of =~ is a variable (my $regexp), then there is a builtin assumption that it uses '/' delimiters which, for my case, are totally unsuitable.

So how do I do this job?

In reply to Regex variables with delimiters by clerew

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