$string="TOPO_DOM 1; /note=Cytoplasmic; /evidence=ECO:0000269|PubMed:24744376; TOPO_DOM 25..74; /note=Extracellular; /evidence=ECO:0000269|PubMed:24744376; TOPO_DOM 100..115; /note=Cytoplasmic; /evidence=ECO:0000269|PubMed:24744376; TOPO_DOM 141..159; /note=Extracellular; /evidence=ECO:0000269|PubMed:24744376; TOPO_DOM 183..227; /note=Cytoplasmic; /evidence=ECO:0000269|PubMed:24744376";

@split_topodom = split(/TOPO_DOM/, $string);
print $split_topodom[0];