sort -u -k 5,5 input_file |                         ##Using sort command on Input_file and sending its standard output as an Input to awk command, read about |(pipe) more in man bash too.
awk -F "\t" '                                       ##Starting awk program here whose input is output of sort command passed to it. Setting -F(field seprator) as TAB here for all lines of Input_file.
(!seen[$12]++ || ! length($12)) && /IPR013087/      ##Checking 2 conditions here. 1st- Either 12th field is coming first time in array named seen OR length of 12th field is ZERO.
'                                                   ##2nd condition is line should have string IPR013087 in it if BOTH conditions are TRUE then print that line.
                                                    ##Since awk works on method of condition then action and we haven't mentioned any action here so when condition is TRUE by default print of current line will happen.