use strict;
my $str = 'setblock ~ ~ ~ minecraft:stone variant=granite aadsdasdsad
execute @e[type=ArmorStand] ~ ~ ~ setblock ~ ~ ~ minecraft:stone variant=granite
';
my $regex = qr/stone *variant=([^\s]*)/ip;
my $subst = 'stone 1';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html