What code have you already written?

Personally, I would extract the "special" symbols and their surrounding whitespace from the first sentence and then replace the elements accordingly in the second sentence:

my %symbols = (
    '/' =>  [],
    '*' =>  [],
    '-' =>  [],
);

$_= "This is a perl script/program.";

push @{ $symbols{ '/' }}, m!(\s*[/]\s*)!;
push @{ $symbols{ '*' }}, m!(\s*[*]\s*)!;
push @{ $symbols{ '-' }}, m!(\s*[-]\s*)!;

my $target= "C'est un perl script / programme";
$target =~ s!\s*([/*-])\s*!shift $symbols{ $1 }!ge;
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