if ( $value =~ m/^([A-Za-z0-9!#\$%&'*+-.^_`|~]+) \s* : \s* (.*)$/x ) {
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Note also that in the
    [A-Za-z0-9!#\$%&'*+-.^_`|~]
character class, the sub-pattern +-. represents | matches the range of characters + , - . which includes the - (hyphen) character.

This seems a bit sus; I wonder if it was intended by the OPer.