my $data = qq(msgagt=ESM_WMB_AIX,sec_id=Sec_id,severity=Low,node=test,msgnode=qwmbap01.xxxxxxxxxxxxx.net,utc=2007-04-26 18:01:59.472+00:00,om=UID=3a7affd6-f420-11db-80b1-000000000000,AlertCode=AEM001,AlertType=AEM-default,AppName=AEM-CommonService2,Message=5004:An error has been reported by the BIPXML4C component.:XML);

my ($msgagt) = $data =~ /msgagt=([^,]+)/;
print $msgagt, "\n";