Perl regex to match but only replace in blocks

Question

This is such a stupid question to ask - but I'm drawing a blank: I have a test string:

Foo|||bar||something|whatever

I need to replace || with |EMPTY_STRING| for each instance.

I'm doing:

s/\Q||/|EMPTY_STRING|/g;

The problem is, that this converts it to:

Foo|EMPTY_STRING||bar|EMPTY_STRING|something|whatever

Notice the || in there. I must be missing something stupid. What is it?

Answer 1

You can use lookaround in your regex:

s='Foo|||bar||something|whatever'

perl -pe 's/(?<=\|)(?=\|)/EMPTY_STRING/g' <<< "$s"

Foo|EMPTY_STRING|EMPTY_STRING|bar|EMPTY_STRING|something|whatever

RegEx Detail:

• (?<=\|) : Lookbehind to assert that we have | behind current position
• (?=\|) : Lookahead to assert that we have | ahead of current position