What is the name of this format?

Here, i perltidy'd your code for you

#!/usr/bin/perl
print qq|<?xml version="1.0"?>|;
print "\n";
while ( $_ = <DATA> ) {

    my $save;
    if ( /^\{FILE\}/ .. /^\{NUMBER\}/ ) {
        unless (/^\{(FILE|NUMBER)\}/) {
            my $filename = $_;
            print "The filename is $filename\n";
        }
    }
    open FH, ">$filename.xml";
    print FH '<?xml version="1.0"?>';
    print FH "\n";

    $_ =~ s/[\cA-\cZ]//g;
    if ( /^{(\w+)}/ ... /^\w+/ ) {
        my $tag = $1 if $1;
        if ( !/^{/ ) {
            print FH "<$tag>$_</$tag>\n";

            #   print FH "<\$tag\>$_\</$tag\>\n";
        }

    }
}
close FH;
__DATA__
^B^B^B^B^B^B
{FILE}
sourcetag1
{NUMBER}
00000
{SOURCE}
source1
{KEYWORD}
{AUTHOR}
author
staff
{FILE}
sourcetag2
{NUMBER}
00001
{SOURCE}
sourcenam
{KEYWORD}
{AUTHOR}
author1
staff1
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