without goto and given/when

Bare blocks are internally one-time while-loops allowing continue-blocks (see perlsyn)

for ("a".."c"){
  {
    print && next if /a/;
    print && next if /b/;
    # here neither a nor b
    last;                  # skip continue-block
  } continue {
    # here either a or b
    print " is in group1"; 
  }
  print "\n"               # all
}
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your free to have more blocks or combining with elseifs or LABEL:s.

UPDATE:

or without fall-through

for ("a".."c"){
  {
    if    ( /a/ ) { print }
    elsif ( /b/ ) { print }
    else          { last }
    print " is in group"; #  a,b
  }
  print "\n"              # all
}
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See also: Re^3: given/when one case prefixes another