Hello,
By hand gbak command looks:
./gbak -user sysdba -password masterkey -BACKUP_DATABASE localhost:/opt/databases/demo.gdb /opt/backup/demo.gdb.gbk
and works fine.
Also in simple script:

chdir ($fbbin);
        system("./gbak -user sysdba -password masterkey -BACKUP_DATABA
+SE localhost:/opt/databases/demo.gdb /opt/databases/demo.gbk")==0 or 
+die "Failed to create backup file \n";
[download]

I see where is the issue with loading details from variables to system command but i don`t have any idea how to fix it.
See:

foreach (@files) {
        chdir ($fbbin);
        print "./gbak -user sysdba -password masterkey -BACKUP_DATABAS
+E localhost:$data$_ $tempdir$_.gbk \n";
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Gives me output:

./gbak -user sysdba -password masterkey -BACKUP_DATABASE localhost:/op
+t/databases/simplemarketing.gdb
 /opt/backup/simplemarketing.gdb
.gbk
[download]

This output should be in one row not in three ;). It looks like enter pressed always after $_ variable loaded from @files table which contains databases filenames. Any ideas how to fix it?