The given regular expression is working fine.

I do not understand this assertion.

>perl -wMstrict -le
"my $rx = qr{^[a-zA-Z]+(['.]?\s*[a-zA-Z]+)*$}xms;
 print '--- output --';
 for (@ARGV) {
   print m{$rx} ? '  ' : 'NO', ' match: ', $_;
   }
"
"all of the following should match"
"FooBar Tech"
"St.John's high school."
"A. B. C. school."
"Institute of management."
"oxford university."
"A.B.C college."
"Ragu ram's college of technology."
"none of the following should match"
"A..B.C college."
"St.John''s high school."
"St.John'.'s high school."
--- output --
   match: all of the following should match
   match: FooBar Tech
NO match: St.John's high school.
NO match: A. B. C. school.
NO match: Institute of management.
NO match: oxford university.
NO match: A.B.C college.
NO match: Ragu ram's college of technology.
   match: none of the following should match
NO match: A..B.C college.
NO match: St.John''s high school.
NO match: St.John'.'s high school.
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