use strict;
my $str = 'Field<OrderByEnumType>("id", null, nullable: true, null);
Field<OrderType>("from_id", null, nullable: true, null);
';
my $regex = qr/Field<([a-zA-Z]+)>\("([a-zA-Z]+)", null, nullable: true, null\);/mp;
my $subst = 'Field(x => x.$2, nullable: true, type: typeof($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