>perl -wMstrict -le
"my $input1 = 'a=1 gibberish b=2 c=3';
 my $match2 =
   '^(?<a>a=(\d)).*?(?<b>b=(\d))?(?<gib>.*?)(?<c>c=(\d))$';
 print qq{input1 '$input1'};
 print qq{Using regex $match2};
 if ($input1 =~ m/$match2/){
   print qq{a '$+{a}'  b '$+{b}'  c '$+{c}'  gib '$+{gib}'}; }
 else { print qq{Input1: didn't match}; }
"
input1 'a=1 gibberish b=2 c=3'
Using regex ^(?<a>a=(\d)).*?(?<b>b=(\d))?(?<gib>.*?)(?<c>c=(\d))$
Use of uninitialized value in concatenation (.) or string at ...
a 'a=1'  b ''  c 'c=3'  gib ' gibberish b=2 '