Re: Efficient way to replace a set of values with another set of values

[tobyink]

Maybe a little something like this?

my $string = q{
1. This is just a sample.
2. This is to check 
3. How a set of values 
4. can be replaced by another 
5. set of values and that too 
6. in the most efficient way.
};
my %replacements = (
    '1.' => 'a.',
    '2.' => 'b.',
    '3.' => 'c.',
    '4.' => 'd.',
    '5.' => 'e.',
    '6.' => 'f.',
);

my $regexp = join '|', map quotemeta, keys %replacements;
$string =~ s/($regexp)/$replacements{$1}/g;

print $string;

[ColonelPanic]

Nice solution. In this case, all cases are at the beginning of the line. It might be a good idea to add an anchor in order reduce the likelihood of false positive matches:

   $string =~ s/^($regexp)/$replacements{$1}/gm;

(The m switch had to added so that ^ would match on each line).

[tobyink]

Indeed. I was in two minds about whether to include it or not. The substitutions in the examples were consistently at the start of lines, but the OP never explicitly specified that that would always be the case, so I decided to go for the more general "anywhere in the string" match.

[ColonelPanic]

Yeah, I agree that it depends on exact requirements. I thought it was worth mentioning though, because it's such a simple pattern that I would be worried about it popping up elsewhere in the data.