use strict;
use warnings;

my $string = <<STRUCT;
 a = 0
 mm struct 
   a = 1
   b = 3
   m1 struct =
     c = 4
     d = 5
     m2 struct =
       f = 9
   e = 7
   m3 struct =
     h = 124
STRUCT

my @lines = split /\n/, $string;
my @levels;
my $ind = 0;
my $oldind;
for( my $i=0; $i<@lines; ++$i ) {
		$oldind = $ind;
		$lines[$i]  =~ /^(\s*)/;
		$ind = length( $1 );
		push @levels, $ind if $i==0;
		$lines[$i] .= ";" if $lines[$i] =~ /\S+\s*=\s*\S+/;
		next if $i==0 or $ind == $oldind;
		if( $ind > $oldind ) {
				$lines[$i-1] .= " {";
				push @levels, $ind;
		} elsif( $ind < $oldind ) {
				while( $levels[-1] > $ind ) {
						pop @levels;
						$lines[$i-1] .= "\n"." "x$levels[-1]."}";
				}
		}
}
while( $levels[-1] > $levels[0] ) {
		pop @levels;
		$lines[-1] .= "\n"." "x$levels[-1]."}";
}

print join "\n", @lines, "\n";